From finding of a titania nanotube, a possibility of producing a nanotube has been investigated on various substances. As a result, production of a nanotube made of titania (TiO2) is confirmed. Titania is one of substances having a photocatalyst activity, and titania in the form of nanotube has a higher photocatalyst activity as compared with that in the form of powder, consequently, various application thereof are expected.
As such a titania nanotube, for example, that having a diameter of from 5 to 80 nm and a length of from 50 to 150 nm is known (Japanese Patent Application Laid-Open (JP-A) No. 10-152323).
However, the titania nanotube described in the publication is not satisfactory for use as an optical sensor and gas sensor.
Under such conditions, the present inventors have intensively studied to develop a titania nanotube suitable as an optical sensor or gas sensor and resultantly completed the present invention. Further, the present inventors have intensively studied also a method for producing a titania nanotube, leading to completion of the present invention.
Namely, the present invention provides a titania nanotube having a length of 1 μm or more.
The present invention provides also a sensor having a titania nanotube having a length of 1 μm or more and an electrode in which the titania nanotube and the electrode are connected.
Further, the present invention provides a method for producing a titania nanotube, comprising a step of dispersing a titania powder in a sodium hydroxide aqueous solution at a temperature of 60° C. or more.
The titania nanotube provided by the present invention is used also as a reinforcing material for metal and resin, in addition to optical sensors and gas sensors. The sensor of the present invention using this titania nanotube may be used for monitoring the condition of plants in the machine industry and chemical industry. Further, according to the production method of the present invention, such a titania nanotube can be obtained easily.